The purpose of this study is to evaluate the growth, and the general, visual, and language development of preterm infants fed different formulas and/or human milk. The formulas vary in the type of fat they contain. Two important fatty acids present in human milk, but not available commercially, are docosahexaenoic acid (DHA) and arachidonic acid (AA). This study will evaluate the effect of adding sources of DHA and AA to formulas. To date there is neither a significant benefit nor disadvantage of feeding AA + DHA in combination to premature infants. Additional data will be available following 12 months of feeding. This controlled randomized parallel study will be conducted at 7 sites around the world.